1. Field of the Invention
This invention relates to the opthalmoscope art and more particularly to an improved coaxially ophthalmoscope having an improved light trap for preventing reflection of unused light into the eye of the viewer.
2. Description of the Prior Art
Ophthalmoscopes utilized for examining the interior structure of an eye have long been know. One class of such ophthalmoscopes is termed coaxial ophthalmoscopes and in such coaxial ophthalmoscopes the axis of viewing the eye under examination coincides with the axis of the light directed into the eye under examination. The advantages of such a coaxial arrangement are, of course, well known in the art. However, in order to provide such a coaxial viewing of the eye under examination it is necessary that the portion of the generated light not directed to the eye under examination be substantially absorbed in order to prevent reflection of this light back into the eye of the viewer. Such devices for absorbing light are generally termed light traps.
The U.S. Pat. Nos. to Tillyer, 1,664,953 and 1,859,756 both show essentially coaxial ophthalmoscope arrangement incorporating a light trap. However, the light trap shown therein has not proven to be sufficiently effective in preventing transmission of the unused portion of the light back into the eye of the viewer.
Similarly, in Tillyer, U.S. Pat. No. 1,889,456 there is a light trap similar to that shown in U.S. Pat. No. 1,859,756.
Other ophthalmoscope arrangements are shown in U.S. Pat. Nos. 3,524,702; 3,543,746; 3,572,910; 3,586,424; 3,600,067 and 3,602,581. However, in none of these patents is there a recognition of the problem inherent in allowing unused light to reflect back into the eye of the viewer nor the necessity for absorbing substantially all of such unused light.